The present invention relates to a key switch for performing an input operation in electronic devices, such as a remote controller, various types of key boards, a cellular phone, a personal digital assistant (PDA), and a digital still camera (DSC).
In the prior art, Japanese Laid-Open Patent Publication No. 2004-220369 describes an example of a key switch used to perform an input operation for an electronic device. The key switch includes a key sheet arranged in a frame for a cellular phone or the like, a movable key top arranged on the key sheet, and a movement amount detector for detecting the movement amount of the key top. The key top is arranged in an opening of the frame. The movement amount detector includes a plurality of magnets, which are arranged on the key top, and a magnetic detection member. The magnetic detection member is arranged on the key sheet and formed by an electric circuit including a magnetic detection sensor, a signal processor such as a central processor (CPU), and wires connecting these devices.
However, water, such as rainwater, and dust may enter the frame from between the opening and the key top. Such water or dust that enters the frame may easily come into contact with the electric circuit on the key sheet. This may short-circuit the electric circuit. Accordingly, the key switch has a shortcoming in that it has low water resistance and low dust resistance.